SCRO / Journées de l'optimisation

HEC Montréal, 29-31 mai 2023


HEC Montréal, 29 — 31 mai 2023

Horaire Auteurs Mon horaire

FTMII Forestry : Tree to market value chains II

31 mai 2023 13h30 – 15h10

Salle: TD Assurance Meloche Monnex (vert)

Présidée par Elaheh Ghasemi

4 présentations

  • 13h30 - 13h55

    Coordination of a Wood Supply Chain for Precise Feedstock Deliveries to a Pulp Mill Digester

    • Zahra Homayouni, prés., PhD student Laval university
    • Luc LeBel, Full Professor at Laval university
    • Lehoux Nadia, Full Professor at Laval university

    One of the major challenges some pulp and paper mills face, especially when they receive a wide diversity of feedstocks for their manufacturing process, is procurement planning. For the fiber procurement department, the capacity to purchase different types of wood species, levels of fiber freshness, and product forms (short and long logs, chips) offers a competitive advantage. Nevertheless, most pulping processes require that a precise and constant mix be fed to the digester (the mill in-feed). Setting an appropriate plan to coordinate wood deliveries is, therefore, necessary to maintain process efficiency. Therefore, the current research tries to identify key concepts that can help managers align supply with demand. The operations considered include purchasing, log transport, external wood yards management, mill yard operations, log chipping process, and chip piles management. The research objective is to investigate approaches to improve the capability of the system to deal with disruptions, uncertainty, and the dynamic operating environment of a large pulp and paper mill. In this presentation, we highlight the problem description and summarize key OR-based methodologies for similar problems.
    Keywords: Wood Supply Chain; Pulp and Paper Industry; Procurement planning; Coordination

  • 13h55 - 14h20

    Strategies to align sales commitments with available supply under uncertainty in the forest supply chain

    • NILOOFAR JAHANI, prés., PhD student at Laval University
    • Luc LeBel, Full professor at Laval University
    • Shuva Gautam, Assistant professor at Laval University

    Producing forest products cost-effectively while satisfying customers’ orders in a short lead time provides a competitive advantage. Like most supply chains, the forest industry comprises suppliers, producers, and customers. Thus, procurement, production, distribution, and sales between interconnected business units are key activities in this supply chain. The Canadian Forest supply chain, due to the challenging environmental conditions, the diversity of products, and numerous suppliers, is complex to manage. One of its main intricacies is related to supply and demand uncertainty. The factors affecting the raw material uncertainty are the natural diversity of forest types and species with complex growing conditions and seasonality, which impacts harvesting and transportation activities. Moreover, market demand and value for the final products vary over time due to economic and political factors. This project focuses on the procurement function at the operational level. It aims to provide a conceptual framework for identifying strategies to align final product sale commitments with available supply resources considering supply uncertainty. By reviewing the existing literature regarding approaches to align supply with variable demand, we can help procurement managers dynamically adjust the wood flow to meet sales commitments in the shortest possible time.

  • 14h20 - 14h45

    Job Scheduling with New Jobs Arising from Degraded Existing Ones: An Application for Forest Firefighting

    • Erdi Dasdemir, prés., Hacettepe University & University at Buffalo
    • Rajan Batta, University at Buffalo
    • Esther Jose, University at Buffalo

    An intriguing subproblem of job scheduling is job scheduling with degradation. We extend this area by considering new jobs resulting from the degradation of existing ones. Our task is to schedule a fleet of mobile servers to process a set of jobs. The existing jobs degrade over time, and if they are not processed promptly, additional jobs are created. Each job causes a value loss and extension of the completion time for the overall problem. We approach this problem as a bi-objective optimization problem, aiming to minimize both the total value loss and the total time spent. The problem aligns with the practical philosophy of "a stitch in time saves nine" and has many real-world applications.

    We focus on implementing this problem in the context of forest firefighting using aerial vehicles. The ignited spots degrade in fire size over time, and if they are not served on time, they spread to neighboring areas. The value of an area decreases as long as the fire continues to burn in it. We aim to identify efficient schedules that include vehicle assignments to fire spots and the routes these vehicles must follow. To tackle this problem, we consider mathematical optimization approaches.

    Keywords: job scheduling, job creation, degradation, aerial forest firefighting

  • 14h45 - 15h10

    Coordination of sales price and production-inventory strategies considering price-sensitive demand: a case study in a Canadian pulp and paper industry

    • Elaheh Ghasemi, prés., Université Laval
    • Nadia Lehoux, Faculty of Science and Engineering, Laval University
    • Mikael Ronnqvist, Faculty of Science and Engineering, Laval University

    The production-inventory-distribution problem considered in this study has been motivated from a real-world problem observed in a multi-product pulp and paper supply chain with multiple customers who are geographically dispersed and will be served by make to stock (MTS), make to order (MTO), or vendor managed inventory (VMI) production-inventory strategies. In order to deal with demand uncertainty, we consider the stochastic demand for customers. Moreover, the actual customer’s demand may vary with different prices offered by the company under different production-inventory strategies which means that the customers have their own price-sensitive demand functions. Here, we develop a two-stage stochastic mixed integer non-linear programming model to coordinate production-inventory strategy selection with pricing decisions under stochastic demand to maximize the expected profit. We consider the strategy selection and pricing decisions as first-stage decisions while production, inventory, and distribution decisions that will be used to evaluate the first-stage decisions are placed at the second-stage decisions. We also design a matheuristic approach based on the Simulated Annealing (SA) algorithm to solve the developed model. We illustrate the applicability of the developed model and the solution approach by using a real case study from the Canadian pulp and paper supply chain and discuss the results.